Question 1191757: A bag contains seven balls numbered 1,2,2,3,3,3 and 4. Let X be the random variable representing the square of selected numbered ball then subtracting 4. Compute the mean and variance of the random variable X.
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website! each has probability of 1/7 of being chosen
add the (squares-1) and divide by 7 to get the expected value
-3,0,0,5,5,5,11
the sum is 23
the expected value is 23/7 or 3.29
variance is sum (square-mean)*prob.
so we have -6.292+3.29^2*2-4+1.71^2*3-4+7.71^2-4
-6.292
6.8241*2
4.7723*3
55.4
that sum is the variance or 77.07
sd is sqrt(V)=8.78
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